Université de Caen Normandie, Inserm, EPHE-PSL, CHU de Caen, GIP Cyceron, U1077, NIMH, 14000 Caen, France.
GIGA-CRC-In Vivo Imaging, Université de Liège and Belgian National Fund for Scientific Research, Liège, Belgium.
J Gerontol B Psychol Sci Soc Sci. 2024 Nov 1;79(11). doi: 10.1093/geronb/gbae152.
Healthy age-related cognitive changes are highly heterogeneous across individuals. This variability is increasingly explained through the lens of spontaneous fluctuations of brain activity, now considered a powerful index of age-related changes. However, brain activity is a biological process modulated by circadian rhythms, and how these fluctuations evolve throughout the day is under investigation.
We analyzed data from 101 healthy late middle-aged participants from the Cognitive Fitness in Aging study (68 women and 33 men; aged 50-69 years). Participants completed 5 electroencephalographic (EEG) recordings of spontaneous resting-state activity on the same day. We used weighted phase-lag index (wPLI) analyses as an index of the functional synchrony between brain regions couplings, and we computed daily global PLI fluctuation rates of the 5 recordings to assess the association with cognitive performance and β-amyloid and tau/neuroinflammation pathological markers.
We found that theta and gamma daily fluctuations in the salience-control executive internetwork (SN-CEN) are associated with distinct mechanisms underlying cognitive heterogeneity in aging. Higher levels of SN-CEN theta daily fluctuations appear to be deleterious for memory performance and were associated with higher tau/neuroinflammation rates. In contrast, higher levels of gamma daily fluctuations are positively associated with executive performance and were associated with lower rate of β-amyloid deposition.
Thus, accounting for daily EEG fluctuations of brain activity contributes to a better understanding of subtle brain changes underlying individuals' cognitive performance in healthy aging. Results also provide arguments for considering the time of day when assessing cognition for old adults in a clinical context.
健康的与年龄相关的认知变化在个体之间存在高度异质性。这种可变性越来越多地通过大脑活动自发波动的视角来解释，现在被认为是年龄相关变化的有力指标。然而，大脑活动是受昼夜节律调节的生物过程，目前正在研究这些波动如何在一天中演变。
我们分析了认知健身衰老研究（101 名健康的中老年参与者的数据；68 名女性和 33 名男性；年龄 50-69 岁）。参与者在同一天完成了 5 次自发静息状态活动的脑电图（EEG）记录。我们使用加权相位滞后指数（wPLI）分析作为大脑区域耦合之间功能同步性的指标，并计算了 5 次记录的每日全局 PLI 波动率，以评估与认知表现以及β-淀粉样蛋白和 tau/神经炎症病理标志物的关联。
我们发现，突显-控制执行互联网（SN-CEN）的θ和γ每日波动与衰老认知异质性的潜在机制有关。较高的 SN-CENθ每日波动水平似乎对记忆表现有害，并且与较高的 tau/神经炎症率有关。相比之下，较高的γ每日波动水平与执行表现呈正相关，并且与较低的β-淀粉样蛋白沉积率有关。
因此，考虑大脑活动的每日 EEG 波动有助于更好地理解健康衰老个体认知表现背后的细微大脑变化。结果还为在临床环境中评估老年人的认知时考虑时间因素提供了依据。
